1. Field of the Invention
The present invention relates to a surface mounting type light emitting diode. In particular, the present invention relates to a surface mounting type light emitting diode attaching importance to heat radiation performance, reliability and productivity, and to a method for manufacturing the same.
2. Description of the Background Art
A semiconductor light emitting element emits visible light or near infrared light in such a manner that a PN junction is formed on an AlInGaP compound semiconductor wafer or a GaN compound semiconductor wafer and forward electric current is fed to the PN junction. In recent years, the semiconductor light emitting element has been widely adopted for use in display, communication, measurement, control and the like. Further, the semiconductor light emitting element tends to be used in a field of automotive components requiring good heat radiation performance and high reliability. There has been also developed a surface mounting type light emitting diode for satisfying such requirements. Examples of such a conventional surface mounting type light emitting diode are disclosed in Japanese Patent Laying-Open Nos. 2006-165138, 2005-183531 and 2003-197974.
As shown in FIG. 19, a conventional surface mounting type light emitting diode 100 includes a chip substrate 101, an LED chip 102 mounted on chip substrate 101, a frame-shaped member 103 formed on chip substrate 101 so as to surround LED chip 102, and a molding resin 104 applied into a recess of frame-shaped member 103.
Chip substrate 101 is a flat and copper-clad wiring substrate, and is made of a heat resistant resin. Chip substrate 101 has, at a surface thereof, a chip mount land 105, a connection land 107, and surface mounting terminals 106 extending from the surface to a bottom face via both end edges. LED chip 102 is joined to a top face of chip mount land 105 of chip substrate 101. Further, LED chip 102 is electrically connected to connection land 107, which is adjacent thereto, by a wire bonding process.
Molding resin 104 is a transparent material such as an epoxy resin, and is applied and cured in the recess of frame-shaped member 103. Chip substrate 101 includes an upper substrate and a lower substrate, that is, has a double-layer structure, which is formed by an Any Layer AGSP (Advanced Grade Solid-bump Process), for example.
As shown in FIG. 20, another conventional surface mounting type light emitting diode 200 includes a lead frame 201, a semiconductor light emitting element 202, a sealing member 203 and a reflector 205. Lead frame 201 has a plurality of lead terminals 204a and a plurality of lead terminals 204b. Semiconductor light emitting element 202 is die-bonded to lead frame 201. Sealing member 203 seals lead frame 201 such that the plurality of lead terminals 204a, the plurality of lead terminals 204b and semiconductor light emitting element 202 are bared. Reflector 205 is attached to sealing member 203 to direct light emitted from semiconductor light emitting element 202 to a certain direction.
Of the plurality of lead terminals, predetermined lead terminal 204a connected to lead frame 201 having semiconductor light emitting element 202 die-bonded thereto is disposed on a side where reflector 205 is placed, and is connected to reflector 205. With this configuration, predetermined lead terminal 204a connected to a portion, to which semiconductor light emitting element 202 is die-bonded, is connected to reflector 205. Thus, heat generated from semiconductor light emitting element 202 is transferred with certainty to reflector 205 via predetermined lead terminal 204a. As a result, the heat transferred to reflector 205 can be efficiently radiated by reflector 205.
In addition, there has been proposed a semiconductor light emitting device for transferring heat generated from a light emitting element to a reflector via a ceramic substrate having a good heat conductivity in order to perform heat radiation.
With regard to heat radiation performance, in conventional surface mounting type light emitting diode 100 shown in FIG. 19, the chip is mounted on small chip mount land 105 and is connected to an electric conductive pattern provided therebelow in a stepwise manner. Chip mount land 105 is small in size, and heat is radiated via electric conductive pattern 108. Consequently, this configuration causes a problem that the heat radiation is unsatisfactory. Furthermore, frame-shaped member 103 of surface mounting type light emitting diode 100 is made of a heat resistant resin. Consequently, this configuration causes a problem that heat radiation performance of frame-shaped member 103 is poor.
With regard to a structure, chip substrate 101 includes an upper substrate and a lower substrate, that is, has a double-layer structure. According to this structure, chip substrate 101 is electrically connected to surface mounting terminal 106, which extends from the top face to the bottom face, with connection land 107 and electric conductive pattern 108 interposed therebetween. In chip substrate 101, consequently, the substrates forming a multilayered substrate must be penetrated successively in order to achieve electric conduction to the lower substrate, which results in a complicated wiring connection pattern.
In conventional surface mounting type light emitting diode 200 shown in FIG. 20, on the other hand, lead terminal 204a connected to the portion, to which semiconductor light emitting element 202 is die-bonded, is connected to reflector 205. This contact area is small, which causes a problem that the heat generated from semiconductor light emitting element 202 can not be transferred with certainty to reflector 205 via lead terminal 204a. In addition, reflector 205 on sealing member 203 made of resin is formed into a plate shape. Consequently, there is a possibility that the heat can not be radiated satisfactorily and efficiently. As a result, this configuration causes a problem that the heat transferred to reflector 205 can not be efficiently radiated by reflector 205.